Alternated Low
and High-Density Turbidity Physical Experiments Highlighting Sediment Wave
Formation Processes
Manica, Rafael1,
Antonio Cosme Del Rey2, Richard Eduard Ducker1, Rogério
Dornelles Maestri1, Ana Luiza de Oliveira Borges1 (1) Universidade Federal do Rio Grande do Sul,
Porto Alegre, Brazil (2) Petrobras
- Petroleo Brasileiro S.A, Vitoria, Brazil
In nature, most of turbidites
sequences are generated by different events that had been being deposited
throughout the years and consequently they present some peculiarities (e.g.
grain size, thickness and bedforms) which difficult
flow-deposit comprehension. In this way physical modelling
has been employed as an alternative tool to understand it. Thus, the present
work shows an experimental simulation of eighteen alternated low (5%
concentration by volume) and high (15% concentration by volume) density
turbidity currents in order to reproduce an analogue of these varied nature
depositional packages. The deposit generated in each single alternated flow have
created a morphologic substratum that interplayed with subsequent flow allowing
the occurrence of erosion processes close the base of deposit (only high
density current) and generating sediment waves whose migrating downstream (at
proximal zones). At distal zone these effects were amortized and tabular layers
were formed. The end member of this processes generate a lenticular
sand bedding geometry. Yet, high-density currents present thicker deposits with
massive gradation whereas low-density showed thinner deposits with predominance
of normal graded bed. However, both flows present sediment waves formation with
coarser grains at lee side and thicker deposits between its toepoint
and troughpoint. The deposit package also shows
similarity with sediment waves developed by natural overspill flows at
meandering channels in mud-rich turbidites systems.
Moreover, the small scale deposit analogous presented in this study is a new
aspect concerning turbidity currents physical simulation proving the usefulness
of this alternative tool in the geological interpretation studies.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California